Wind turbine power generating apparatuses have become increasingly popular in recent years in view of preservation of the global environment. Especially, large wind turbine power generating apparatuses, which are advantageous in improving power generation efficiency, have been planned to be launched on water such as ocean or lakes in various regions.
As a wind turbine power generating apparatus installed on the water, a floating-body type wind turbine power generating apparatus with a wind turbine built on a floating body which floats on the water surface is known. There is a large floating-body type wind turbine power generating apparatus with a tower having a height of several tens of meters to more than a hundred meters. In such a floating-body type wind turbine power generating apparatus, it is extremely difficult to access a high altitude such as the top of the tower, a nacelle or a hub of the wind turbine while the wind turbine power generating apparatus is on the water upon maintenance, installation, deconstruction, or the like.
In this regard, Patent Document 1 discloses a method of submerging a tower of a wind turbine to make the tower contact the sea bottom upon maintenance, in order to facilitate access to an upper section of the wind turbine. Further, Patent Documents 2 and 3 disclose configurations in which a tower of a wind turbine is submerged in a spar upon maintenance.